1. Field of the Invention
The present invention relates generally to conduit or pipe couplings, and in particular to a system, tool and method for pushing the ends of a pair of plastic conduit sections into a coupling to form a fluid-tight, pull-out resistant coupling therebetween.
2. Discussion of the Related Art
Couplings and fittings of various types are used for joining pipes and conduits. Examples include threaded fittings, couplings that are secured with solvent adhesives, weldments and various push-type couplings. The performance criteria for pipe coupling mechanisms are generally determined by such factors as the pipe materials, design pressures, temperature ranges, fluid-tight requirements, pull-out resistance requirements and environmental conditions.
For example, the nationwide, fiber-optic, telecommunications networks consist largely of buried fiber-optic cables. The cables are commonly protected from groundwater and other subsurface conditions by enclosing them within plastic conduits. A common fiber-optic cable installation procedure involves placing the empty conduits below grade with special trenching and tunnel-boring equipment, whereafter the fiber-optic cables are blown through the conduit with high-pressure air. The plastic conduits and the connecting fittings used in such installations must be impervious to groundwater, resistant to the corrosive effects of soil and capable of maintaining relatively high internal air pressures. Therefore, the connecting fittings or couplings used for joining the conduit sections require sufficient pull-out resistance to withstand internal air pressures, and further to resist tensile forces tending to separate the conduit sections by pulling apart their connections.
Conduit coupling systems are commonly used in adverse field and environmental conditions where only minimal equipment is available and speed is relatively important. Therefore, machining and other preparation of the conduit sections ends should be eliminated or minimized. Manually-operated hand tools are generally preferred due to their portability and independence from external power sources. Moreover, the couplings and other fittings should be relatively simple, inexpensive, strong and reliable. Still further, the bores of the aligned conduit sections should be free from obstructions after they are coupled.
Heretofore there has not been available a conduit coupling system, tool and method with the advantages and features of the present invention.